Cadillac Repair/gas cap


my driver information center displays "gas cap" and the service engine light is on. I replaced the gas cap but it still shows "gas cap". how do I check the codes to find out what is causing this.


You did not supply the year and model, but the codes are not going to tell you anything more than what you know right now. The codes are general and do not give you an exacting cause. If the vehicle is 1994 or newer, a service gaage (not a dealer) can attach a Tech II scanner to the vehicle's computer to give you pin point accuracy on exactly what the problem is. Otherwise you end up chasing ghosts replacing perfectly good components that were not the problem.

You did not say if this problem just started or if it had been going on for a while. There could be a plugged vent hose or something else going on.

The check engine and fuel cap are related telling you thee is some sort of emissions problem. With the check engine light illuminated, fuel mileage and performance will suffer and it is not just a matter of getting the light out. The problem needs to be repaired first.

Personally, I would prefer just an emissions light came on without telling the driver a general diagnoses, because like what happened to you, you spent the money on a fuel filler cap that you did not have to spend because replacing it did not fix the problem.
This may be a minor repair, but it needs to be properly diagnosed first.

Good luck.

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Rob Painter


Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?


Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.

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